Cut resistant tire

Abstract: A cut resistant pneumatic tire is provided. The tire has a monofilament wire structure embedded in or under its tread or sidewall, and is used in off the road applications such as mining. The monofilament (22a,22b) wire has a diameter of 0.4 to 1.2mm and is made of brass plated steel. The wire may be woven or may have a spring link configuration. Two monofilament wires may be twisted together, and when two such wires are used, the total diameter is 0.8 to 1.4mm.

Description: BACKGROUND OF THE INVENTION The invention relates to cut resistant pneumatic tires, especially off-the-road tires and heavy duty off-the-road tires having typically 1 to 36 carcass plies and 6 belts (in a radial ply tire) or 4 breakers (in a bias ply tire), and one to four sets of beads. Heavy duty off-the-road tires, because of the nature of their use, are exposed to cutting and delamination caused by sharp rocks and uneven terrain. In the prior art, this problem was sometimes addressed by including wire fragments embedded in the rubber of the tread and sidewalls of such tires. Although shredded wire has been tried to prevent cut growth, it does not work well, and may be relatively expensive (brass coated wire works best), and is very difficult to handle and process into rubber. Shredded wire tends to jam the processing equipment and causes accelerated wear of the processing equipment. This problem was addressed in EP-A-481913 by incorporating RFL coated monofilament fibers into the tread rubber and sidewall rubber of mining tires. It is an object of the present invention to provide a cut resistant tire, which is easier to process and to build than a tire reinforced with shredded wire. Other objects of the invention will be apparent from the following specification and claims. PRIOR ART U.S. Patent 122,249 to Brandenburger relates to a tire having a carcass comprising a chained structure which interlocks both beads of the tire. The rings of the chain are made of spring steel wire and the construction is described as being armor or a metallic fabric. U.S. Patent 1,143,265 to Gautier relates to armoring pneumatic tires, and describes a structure similar to a bicycle chain comprising the carcass reinforcement of the tire. U.S. Patent 1,201,257 to Cobb relates to a fabric for tires in which longitudinal wire cords or filaments are interwoven with organic fibers. The structure described is used in a crown area of the tire as a belt structure. U.S. Patent 1,207,709 to Campbell relates to fabric for tires in which wire is interwoven with organic cords or fibers in a wire/organic composite structure. U.S. Patent 1,228,650 to Christian relates to a pneumatic tire in which a woven wire fabric is used in the crown area and upper sidewall of the tire. The woven wire structure is said to provide resistance against perforation, lines 17-18, and blowouts resulting from high internal pneumatic pressure, and from injury termed "stone bruise", lines 27-30. U.S. Patent 1,236,227 to Stewart relates to an armored tire structure which comprises a series of interconnected rings which also interconnect with the beads of the tire. The rings are described in the specification as being a series of chains disposed transversely within the body of the shoe. US-A- 1,271,388 (Taylor) relates to a tire shoe or casing which comprises metal strands, preferably woven together. US-A- 1,365,208 (Sacks) relates to a tire casing which comprises a circumferentially endless knitted fabric. The fabric is said to be flexible wire at column 1, line 51. US-A- 1,602,870 (Villiers) relates to a sheet material for covering, lining, or closing constructions of all kinds, particularly bomb-proof awnings. The structure comprises woven wire in a rubber composite. US-A- 2,987,095 (Toulmin, Jr.) relates to a tire cord structure and describes a tire wherein reinforcing metal is incorporated and thoroughly united with the rubber in the body of the casing. The individual strands may be woven to provide a fabric structure or interwoven middle layer, column 2, lines 43-45. US-A- 4,235,274 (Suzuki et al.) relates to a tire structure having a reinforcing layer composed of a helically formed filament or bundle of wire in the crown area of the tire. According to the claims, the bundle comprises at least two filaments and in use in a tire, it appears that five to seven filaments comprise the bundle used. EP-A- 598 215, published on 15.5.1994 and falling under Art. 54(3) and (4), discloses a cut resistant tire having a monofilament wire structure embedded in or under its tread or sidewall. The monofilament has a diameter of 0.4 to 1.2 mm and is made of brass plated steel. The wire may be woven or two monofilament wires may be twisted together. SUMMARY OF THE INVENTION A cut resistant pneumatic tire is provided as defined in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates a heavy duty off-the-road radial tire having a wire filament structure embedded therein. Fig. 1A illustrates a cross section of a radial ply tire having woven monofilament wire embedded therein. Fig. 1B illustrates a perspective cut-away view to illustrate the independence of nonwoven wires in separate layers in a radial ply tire. Fig. 2 illustrates a cross section of a bias ply tire having nonwoven monofilament wire embedded therein. Fig. 3 illustrates individual wires embedded in rubber. Fig. 4 illustrates two monofilaments twisted together. Fig. 5 illustrates a structure for monofilament woven wire that can be used in the tire. Fig. 6 illustrates a structure for linked springs that can be used in the tire. DETAILED DESCRIPTION OF THE INVENTION With reference now to Figs. 1, 1A, 1B and 2, embodiments of a heavy duty, off-the-road tire 10 of the invention are illustrated. The tire comprises beads 12, carcass plies 14 wrapped around beads 12, belts 21 and tread base 16 disposed over carcass plies 14 in a crown area of tire 10, tread 18 disposed over tread base 16, and sidewalls 20 disposed between the tread and beads 12. Wire 22 is embedded in or under the tread and the sidewall 20. Fig. 1 represents a radial tire having one set of beads, and Fig. 2 represents a bias ply tire having four sets of beads. In the illustrated embodiment, wire 22 has a diameter of 0.4 to 1.2mm and is made of brass coated steel. The tensile strength of the wire used is 1300 to 3500 MPa, preferably 1350 to 3250 MPa. The elongation of the brass coated wire, before incorporation in an armor structure, was 2 to 8%. Those skilled in the art will recognize that the structure of the wire, especially when a spring structure is used, will significantly increase the potential elongation. Examples of monofilament steel wire which can be used in the invention are 1040c steel wire with a tensile strength of 1365 MPa, and 1092c steel wire with a tensile strength of 1820 MPa. As used in the illustrated embodiments, the wire was preformed into its desired structure by Justesen Industries, 1090 Yew Ave., Elaine, Washington 98230, and by National Standard, Corbin, Kentucky 40701. Continuous lengths of wire are used in various components of the tire. As used herein, continuous wire means; of a length at least sufficient to (continuously) span the treadwidth or sidewall width (or both together) of the tire, or to form a chain link or similar structure; and is distinguished from shredded wire. The wire can be used in the tire at an end count of, theoretically, 8 to 120 ends per 10 cm (2 to 30 epi), although end counts of 12 to 40 ends per 10 cm (3 to 10 epi) are believed sufficient. In the illustrated embodiments, end counts of 12 to 24 ends per 10 cm (3 to 6 epi) are preferred, and in two preferred embodiments 12 and 16 ends per 10 cm (3 and 4 epi) were used, to provide the proper rivet as well as the strength and penetration resistance required. The wire is brass plated or coated using conventional techniques. With reference to Fig. 3, the wire may be calendered so that the wires 22 are embedded in a layer of rubber 40, independent of one another, or two wires can be twisted together, with a 12 to 25mm lay length as illustrated in Fig. 4. As illustrated in Fig. 1A and 1B, in a radial ply tire the wires may be woven or nonwoven, and the nonwoven calendered rubber sheets containing parallel monofilament wire, illustrated in Fig. 3, cover the carcass plies from bead to bead (Fig. 1B). As will be apparent to those skilled in the art, the wires may be applied from bead to bead in one sheet. In the illustrated embodiment, a first calendered rubber sheet 22b extends from a first bead over a first sidewall and a first shoulder 23 of the tire and over the belts 21 (i.e. across the crown of the tire) to a second shoulder of the tire, and a second calendered sheet extends from a second bead over a second sidewall and said second shoulder and across the crown to said first shoulder of said tire. With reference to Fig. 2, in a bias ply tire, the monofilament wires 22a may form an angle of 10° to 170° with respect to the equatorial plane of the tire. In the illustrated embodiment, the wires in the first sheet are at an angle of 10° to 80° with respect to the EP, preferably 45°, and the wires in the second sheet are at an angle of -10° to -80° (which corresponds to 100° to 170°), preferably -45° with respect to the EP. Such independent sheets of calendered monofilament wire are used in applications where the wires tend to move in the building of the tire, such as in bias ply tires, since woven wire will not pantograph to the extent needed in such applications. Two to four calendered sheets of independent monofilament wire may be placed on top of one another in the tire. In a preferred embodiment, the wires will be formed or combined in an armor type structure so that the wires work together and support each other in the tire structure. The structure provides flexibility as well as strength and penetration resistance. The wire is brass plated, preferably before incorporation into the armor structure. The armor structure may comprise interconnected rings, chain links, woven structures, interlocking springs, or any other such structure known in the prior art. With reference to Fig. 5, in one embodiment, the wire may be woven having wires in a "weft" direction at an angle of about 90° with wires woven in a "warp" direction. Those skilled in the art will recognize that the woven wire structure may also be pantographed such that an acute angle between wires of intersection may be from 30° to 89°. Consequently, an obtuse angle in the pantographed woven structure will be from 91° to 150°. In a preferred embodiment, the wires will be woven at a 90° angle and placed in the tire construction at substantially a 45° angle with respect to the equatorial plane of the tire. When the tire expands in the mold during the manufacturing process, the woven structure pantographs slightly, making possible the expansion of the wire structure together with the expansion of the tire. In an alternative embodiment, the intersections 24 of the wires may be fused (see Fig. 5), providing a structured relationship whereby adjacent wires provide support for individual wires. The inherent flexibility of the wires provide a flexibility to the structure as a whole. In the manufacture of a tire with such a structure, an overlap splice may be used, and the structure expands by slipping at the overlap splice during the molding of the tire. With reference now to Fig. 6, wires 22b may be coiled into a spring, and the wires may be interlocked by causing each coil 26 of a spring to have an interlocking relationship with a coil of an adjacent spring. In such a structure, the individual springs move independently of one another, but have a limited range of motion such that the structure as a whole has substantial flexibility within the limited range, but the structure has great strength and resistance to distortion at the limits of the range. It is preferred that the structure containing the interlocking springs be applied to the tire such that the individual springs have an angle of substantially 45° with the equatorial plane of the tire, and the structure is applied using an overlap splice. The structure will slip at an overlap splice, allowing the expansion needed, during the molding of the tire. The tires 10 of the invention may be built as is conventional in the art except that the wire structure, for example structure 22a or structure 22b, can be rolled onto the tire in the same manner as a belt ply before application of the tread. The wire may be rubber coated by calendering prior to application. Alternatively, the wire may be applied to the tire as manufactured, and the rubber of the tread and/or tread base will flow around the wire in the molding of the tire. The brass coating on the wire assures good adhesion between the wire and the rubber of the tread base and/or tread.

Claims: A heavy duty pneumatic tire (10) comprising at least a pair of parallel annular beads (12), carcass plies (14) wrapped around said beads, reinforcement plies (21) disposed over said carcass plies in a crown area of the tire, a tread (18) comprising a tread cap and a tread base (16) disposed over said reinforcement plies (21), sidewalls (20) disposed between said tread (18) and said beads (12), and continuous monofilament wires (22) having a diameter of 0.4 to 1.2mm included in or under said tread and sidewalls, wherein said monofilament wires (22) cover said carcass plies (14) from bead to bead and wherein said monofilament wires form an angle of 10° to 170° with respect to the equatorial plane (EP) of the tire. The tire of claim 1 wherein said continuous monofilament wires (22) are arranged in an armor structure. The tire of claim 2 wherein said monofilament wires (22a) are woven and wires in the weft direction have the same diameter as wires in the warp direction. The tire of claim 3 wherein said warp and weft wires (22a) are fused together at their points of intersection. The tire of claim 3 or 4 wherein said wires (22a) are woven at a density of 12-24 ends per 10 cm (3-6 epi) in the warp direction and at the same density in the weft direction. The tire of claim 2 wherein said monofilament wires (22b) are coiled into the shape of a spring and are interwoven with similar wires to provide a linked structure. The tire of any of claims 1-4 and 6 in which said wire (22) has a tensile strength of 1300 MPa to 3500 MPa, and wherein said steel wire is brass coated and has, before incorporation in a wire structure, an elongation of 2 to 8%. The tire of claim 1 wherein two monofilament wires (22) are twisted together and have a total diameter of 0.8 to 1.4mm. The tire of claim 1 wherein paralell monofilament (22) wires are calendered into rubber sheets and wherein two to four calendered sheets are placed on top of one another in said tire (10). The tire of claim 9 wherein a first calendered rubber sheet extends from a first bead (12) over a first sidewall (20) and a first shoulder (23) of the tire and across the crown to a second shoulder of the tire, and a second calendered sheet extends from a second bead over a second sidewall and said second shoulder and across the crown to said first shoulder of said tire.

Inventors: HOBART PAUL WILLIAM, MALIN JERRY, MASSIE II JOHNNY DALE, REISINGER RICHARD HENRY, HOBART, PAUL WILLIAM, MALIN, JERRY, MASSIE II, JOHNNY DALE, REISINGER, RICHARD HENRY
Applicants: GOODYEAR TIRE & RUBBER, THE GOODYEAR TIRE & RUBBER COMPANY
Application year: 1994
Main classification: B60C9
IPC codes: B60C9, B60C15